Cylindrical lithium secondary battery and method of fabricating the same

Abstract

A cylindrical lithium secondary battery includes an electrode assembly formed by stacking a first electrode plate having a first electrode tap, a second electrode plate having a second electrode tap, and a separator interposed between the first and second electrode plates. The first electrode plate, the second electrode plate and the separator are wound to form the electrode assembly. The secondary battery also includes a case for storing the electrode assembly and a cap assembly combined with an upper portion of the case to sealing the case. The radius of curvature of the second electrode tap is greater than the radius of curvature of the first electrode tap.

1. A cylindrical lithium secondary battery comprising:
 an electrode assembly including a first electrode plate comprising a first charge collector having a longitudinal axis extending in a first direction and a first electrode tap having a longitudinal axis extending in a second direction substantially perpendicular to the first direction, wherein the first electrode tap protrudes from the first electrode plate, a second electrode plate comprising a second charge collector having a longitudinal axis extending in the first direction and a second electrode tap having a longitudinal axis extending in the second direction, wherein the second electrode tap protrudes from the second electrode plate, and a separator between the first electrode plate and the second electrode plate, the first electrode plate, the second electrode plate and the separator being wound; 
 a case housing the electrode assembly; and 
 a cap assembly sealing the case and comprising a deformable safety vent, wherein the first electrode tap electrically contacts the deformable safety vent; 
 wherein the first electrode tap and the second electrode tap each have a bar imparted radius of curvature. 
 
     
     
       2. The cylindrical lithium secondary battery of  claim 1 , wherein the first electrode tap or the second electrode tap is at a winding start position. 
     
     
       3. The cylindrical lithium secondary battery of  claim 1 , wherein the bar imparted radius of curvature of the second electrode tap at a winding end position is greater than the bar imparted radius of curvature of the first electrode tap at a winding start position. 
     
     
       4. The cylindrical lithium secondary battery of  claim 1 , wherein the bar imparted radius of curvature of the first electrode tap at a winding start position is between about 0.5 mm to about 2.5 mm and the bar imparted radius of curvature of the second electrode tap at a winding end position is between about 8.0 mm to about 20.0 mm. 
     
     
       5. A method of fabricating a cylindrical lithium secondary battery comprising:
 attaching a first electrode tap having a longitudinal axis extending in a first direction to a first electrode plate comprising a first charge collector having a longitudinal axis extending in a second direction substantially perpendicular to the first direction such that the first electrode tap protrudes from the first electrode plate in the first direction; 
 attaching a second electrode tap having a longitudinal axis extending in the first direction to a second electrode plate comprising a second charge collector having a longitudinal axis extending in the second direction such that the second electrode tap protrudes from the second electrode plate in the first direction; 
 interposing a separator between the first electrode plate and the second electrode plate; 
 forging or rolling the first electrode tap and the second electrode tap with a bar to impart a curvature thereto; 
 winding the first electrode plate, the second electrode plate and the separator into an electrode assembly using the first electrode tap as a winding start position; and 
 inserting the electrode assembly into a cylindrical case; 
 wherein a radius of curvature of the second electrode tap is greater than a radius of curvature of the first electrode tap. 
 
     
     
       6. A method for providing a substantially cylindrical jelly-roll wound electrode assembly for a cylindrical lithium secondary battery having a center axis, comprising:
 stacking a first electrode plate, a separator and a second electrode plate as an unwound electrode assembly, wherein the unwound electronic assembly has a longitudinal axis extending in a first direction; 
 forging or rolling a first electrode tap having a first longitudinal axis with a bar to impart a radius of curvature corresponding to a first axial radius about the center axis; 
 forging or rolling a second electrode tap having a second longitudinal axis with a bar to impart a radius of curvature corresponding to a second axial radius about the center axis, the second axial radius being larger than the first axial radius; 
 placing the first electrode tap at a winding start position on the first electrode plate of the unwound electrode assembly such that the first electrode tap protrudes from the first electrode plate along the first longitudinal axis in a second direction substantially perpendicular to the first direction; 
 placing the second electrode tap at a winding end position on the second electrode plate of the unwound electrode assembly such that the second electrode tap protrudes from the second electrode plate along the second longitudinal axis in the second direction; and 
 winding the unwound electrode assembly about the center axis into a jelly-roll wound electrode assembly.